Multi-Product Tank

ABSTRACT

A means of storing multiple bulk liquids inside one storage tank which involves the installation of flexible internal tank(s) where such internal tank(s) comprise at least partially rigid end caps ( 12 ) and flexible membrane side walls ( 14 ), and/or internal bladders ( 15 ). Theses internal tanks and/or bladders are compatible with physical conditions of large bulk storage tanks ans potentially capable of storing thousand of tons. The development of multi-product tanks allows tank-farm operators great flexibility in the logistical operation of storing a range of incompatible liquids, and avoids exhaustive tank clean out procedures that are normally required when switching large tanks from one product to another product, especially where incompatible specifications are intolerant of cross-contamination.

This application claims the benefits of provisional application Ser. No.60/820,415 and provisional application Ser. No. 60/820,425, both filed26 Jul. 2006, and each of which is incorporated herein by reference inits entirety.

TECHNICAL FIELD

The present invention relates to means of storing multiple bulk liquidsinside one storage tank and, more particularly, involves use of internaltank(s) that compose at least one liquid-tight, flexible membrane orbladder.

BACKGROUND OF THE INVENTION

A number of processing industries require the use of multi-tank storagefacilities to store feed stocks, intermediates and products. Inparticular, the processing of crude oil into a wide range of petroleumproducts and by-products requires the use of expansive multi-tankstorage facilities called “tank farms.” Depending on the processingbeing performed, these tank farms may range from several dozen tanks toseveral hundred tanks, many of which have storage capacities in excessof 50,000 cubic meters.

Due in part to the efforts to produce environmentally friendly productswith very low levels of environmentally sensitive components, such assulfur, a refinery must take extreme care not to cross-contaminate theproduct streams, either through residues in pipe work or when changingthe use of one tank between different products. While it is practical tochange the use of one tank from one liquid to another liquid withlargely incompatible properties or specifications, it is not a processthat can be implemented with out considerable delay (such as weeks) andcleaning expense. Such a change over generates large volumes ofcontaminated petroleum requiring reprocessing and requiring staff toenter and work inside a potentially hazardous environment.

Additionally, the operational logistics of a tank farm are complex.These facilities may be accepting super-tanker volumes of crude oil fromdifferent origins that require careful blending or totally separateprocessing. The delivery quantities are also fixed which can result inpartially-filled tanks, e.g. only 10% of a 50,000 cubic meter tank isused for a short period. The ability to utilize 10% spare capacity inanother tank, for example, one already 70% full with a different liquid,would be a real advantage.

Further, an oil refinery's tank farm must also handle wide fluctuationsin product storage due to changing seasonal demands. For example thedemand for heating oil can change rapidly with the onset of winter andthe formulation of certain transportation fuels is often regulated tochange between seasons. Accordingly, there is a need to store two ormore liquids in a tank in order to fully utilize all tank volumes whilepreventing any cross-contamination. The ability to store two or moreproducts in the same tank simultaneously can greatly simplify thestorage logistics and reduce the total number of tanks required. Thislast point is significant because most refineries are in need ofexpanding capacity and are also faced with some degree of land lock, dueto a combination having close neighbors and the high cost of approvaland construction of additional tankage.

There are many examples of placing one container within anothercontainer, the most obvious example in the oil industry being the use ofdouble hulled super-tankers and the use of flexible bladders withinrigid automotive fuel tanks (U.S. Pat. Nos. 3,968,896, (Giacoletti etal.); 3,949,720, (Zipprich et al.); and 6,360,729 (Ellsworth)). In thesereferences, the purpose of the double containment is not for the purposeof storing multiple products in the same container, but more alignedwith the goals of personal end environmental safety.

U.S. Pat. No. 4,818,151 (Moreland) discloses a containment system wherethe purpose is to increase safety by providing an additional barrier tocontain leakage. In this example, a rigid under-ground storage tank isencased by a flexible bladder. Similarly, U.S. Pat. No. 4,763,805(Strock) describes the use of a flexible bladder inside an undergroundstorage tank designed to comply with secondary containment laws thatprevent leakage from primary tank.

U.S. Pat. No. 3,943,873 (Hering et al.) is an example of multipleflexible bladders used in a ship's hall. Here, two separate bladders areused to create three separate compartments, two being used to hold oilon either side of the hull and the third central compartment to holdballast water, such that the hydraulic instability of a partial load ofoil in the hull is minimized.

U.S. Pat. No. 6,152,059 (Del Raso) is another example of flexiblebladders being used to contain oil in a ship's hull. Here, the purposeis to provide an emergency containment, and should the integrity of thehull be compromised, then pumping systems can be used to transfer theoil into the flexible bladders to limit leakage.

There is a need for a multi-product tank system that permits the storageof multiple liquids in a tank thereby allowing maximum use of tankvolumes and minimizing the cleansing requirements between storingincompatible liquids.

SUMMARY OF THE INVENTION

This invention relates to the disposition of a separate container orcontainers within a storage tank, wherein the internal container orcontainers are used to isolate at least one liquid from another liquidcontained in the tank. To this end, present invention provides for amulti-product storage tank that comprises a tank shell, a support meanssuch as a porous wall or screen capable of encircling a bladder disposedwithin the support means where such support means is attached to theinside of the tank shell. This structure permits the storage of a secondliquid within the bladder and the storage of a first liquid within thespace between the inside of the tank shell and the exterior of thebladder.

In one aspect the invention provides a multi-product storage tankcomprising: (a) a first tank shell comprising a bottom and a side wallextending upwardly from the bottom thereby adapting the shell to containliquid; (b) a second tank disposed within the first tank wherein thesecond tank comprises at least one partially rigid end cap and flexible,fluid-tight, membrane side wall attached to the end cap thereby defininga first space between the first tank shell and the second tank wherein afirst liquid can be stored in isolation from the contents of the secondtank.

In another aspect the invention provides a multi-product storage tankcomposing: (a) a first tank shell comprising a bottom and a side wallextending upwardly from the bottom thereby adapting the shell to containa first liquid; (b) a support means disposed within the tank shell andfixed to the tank shell: and (c) a flexible, fluid-tight bladderdisposed within the support means, wherein the flexible bladder isadapted to storing a second liquid, thereby passing a first spacebetween the first tank shell and the flexible bladder wherein a firstliquid can be stored in isolation from the contents of the bladder.

In another aspect, the present invention provides for a multi-productstorage tank having a novel configuration wherein a first rigid tank isprovided to include a second internal tank wherein the second tankcomprises at least one end cap wherein a portion of such end cap or endcaps is rigid or semi-rigid and wherein the side walls of the secondtank are fabricated with a flexible membrane material. This structurepermits the storage of a second liquid within the second tank and thestorage of a first liquid in the space between the inside of the rigidtank and the exterior of the second tank.

In specific aspects, this invention permits the storage of multiplepetroleum products in one large storage tank, thus increasing theflexibility of storage options for a petroleum refining facility;however the invention has much wider industrial applications in otherindustries where liquid storage is required.

This invention provides a flexible storage system for tank farms byenabling multiple, potentially incompatible liquids to he stored in onetank. This results in multi-product tanks that can have the ability tostore different liquids either simultaneously or sequentially with theadded advantage of eliminating or reducing between-use cleanings.

Additionally, this invention provides means for the ability toseparately fill or discharge the second liquid from the bladder and thefirst liquid from the tank disposed in the space between the tank shelland the bladder.

Where flexible bladders are used, this invention can comprise a,membrane with sufficient tensile strength and chemical compatibility toensure long-term separation of the applicable liquids. The bladder(s)can be connected to separate supply, sampling and discharge lines andessentially act as separate tank(s). The limitation being that thecombined volume of the internal bladder or bladders and the primary tankmust not exceed the volume of the primary tank alone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an internal floating tank arrangement disposed within tank3 where the end-caps 12 are rigid and the cylindrical side wall 14comprise flexible, fluid-tight membrane material.

FIG. 2 shows an internal floating tank arrangement disposed within tank3 where the end-caps are comprised of a rigid annulus 15 and a flexible,liquid-tight membrane 13 and again, the cylindrical side wall 14comprises flexible material.

FIG. 3 shows an internal floating tank arrangement similar to FIG. 2where the end-caps are comprised of a rigid annulus 15 and a flexiblemembrane 13; however, in this case the floating tank storing an isolatedliquid is partially restrained by a porous wall 70. Such a restrainingwall may vary considerably in size, and can encircle the entire secondtank, or it could be a relatively small barrier to shield the internalsecond tank from highly turbulent flows during the filling of the firstor second tank. The porous wall can be composed of a rigid wall ofperforated metal or other suitable polymer or composite material, orcomprise of a flexible wall such as a chain-linked fence or equivalentmesh like material that is suitably restrained to minimize contact withthe inner wall of the outer tank. Such a restraint may be include amaterial having a very low level of rigidity such as an open-cell foamsimilar to that used for safety in gasoline tanks of racing cars.

FIG. 4 shows a first tank 3 wherein stored liquids are isolated by meansof end cap 18 and a flexible conical side wall 16 attached to the insidewall of the first tank. The smaller end of the flexible conical sidewall 16 is connected to the end cap. The first tank 3 has a dischargeand filling means 20 that is in flow communication with the liquidlocated below the end cap.

FIG. 5 shows an arrangement very similar to that shown in FIG. 4, anddetails conduit 17 that is suitable for the filling and the discharge ofthe liquid located above the end cap.

FIG. 6 shows how the arrangement in FIG. 5 can be configured toincorporate a floating roof 48. The larger end of the flexible conicalside wall 16 is attached to the floating roof.

FIG. 7 details an internal second tank having flexible cylindrical sidewall attached to the base of a rigid first tank 3 and to a roof 63. Thesecond tank isolates the contained liquid 7 from another liquid 5 withinthe first tank. The second tank has a discharge and filling means 49that is in flow communication with the liquid 7. The first tank 3 has adischarge and filling means 21 that is in flow communication with theliquid 5. Roof 62 can comprise of a combination of rigid and flexiblematerials.

FIG. 8 details an arrangement similar to that shown in FIG. 7, whichincludes two optional membranes 80, 81 disposed to allow full dischargeof the first liquid 5 while maintaining a quantity of second liquid 7 instorage. In this case, either or both optional membranes should befilled with a liquid such as process water through filling and dischargemeans 82 and 83, thereby providing hydraulically support to the flexiblecylindrical side wall 61, and aid in discharge of the surrounding liquid5, which would otherwise be trapped between the outer tank wall and theinner flexible tank wall. Furthermore, this arrangement not onlyrelieves the expansion stresses on the flexible cylindrical side wall 61when the outer liquid 5 is drained below the roof of the inner tank, butalso provides a smooth lubricated surface 80 and 81 for the innerflexible side wall to slide vertically as it is filled or discharged.

FIG. 9 depicts a cross-section through a perspective view of anotheraspect of the multi-product tank of the present invention. Outer tank 3has a discharge and filling means 2 that is located between an outer,liquid-tight cylindrical tank wall 3 and an inner, cylindrical, porouswall 70. The porous wall is depicted as a cylinder of perforated metalplate affixed to the base of the tank 3. Secondary liquid is containedwithin bladder 15, which is restrained by the porous wall 70. Bladder 15is shown with two of its primary connections, a fill and discharge port4 and a vent conduit 1 to control the buoyancy effects of gases that maybe present.

FIG. 10 shows a plan view of a tank similar to FIG. 9; where theflexible cylindrical side wall of the bladder is partially restrained bya porous wall 70. Such a restraining wall may vary considerably in size,and can encircle the entire bladder, or it could be a relatively smallbarrier to shield the bladder from highly turbulent flows during thefilling of the tank or bladder within the tank.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides a more flexible set of storage logistics for theoperation of tank farms by enabling two or more, potentiallyincompatible liquids to be stored in one tank. To this end novelconfigurations of a rigid tank are provided that in one aspect includesa secondary internal container with flexible surfaces such as a bladdercapable of allowing the bulk of the secondary container to be dischargedseparately from the contents of the primary, outer, rigid tank. Inanother aspect, at the invention discharged. Such can be employed in theconversion or retrofitting of single-use tanks into multi-product tanksthat have the ability to store different liquids either simultaneouslyor sequentially with the advantage of eliminating between-use cleaningthat may consume weeks of tank down-time while providing efficient useof tank volume.

In one aspect of this invention addresses the needs of petroleum tankfarm operators, where most at the tanks are thirty to sixty meters ormore in diameter, where the time and effort required to clean theselarge tanks between multiple product storage tasks is not insignificant.The invention, however, is applicable across a wide range of industriesand tank sizes.

The second tank disposed with the first tank may be comprised of certainrigid elements in combination with flexible elements. For example, FIG.1 shows an embodiment of the invention where rigid end caps are attachedto a flexible membrane cylindrical section. Further in FIG. 2, showsrigid disk end-caps comprised of a rigid annulus with an inner, flexiblemembrane. In a preferred embodiment of the invention, the flexiblemembrane would be a fiber reinforced polymer such as urethane, which mayor may not include a metallic or other impervious inner layer. Clearly,many structural combinations of this invention can be developed by thoseskilled in the art without detracting from the novelty or benefits ofthe invention.

Another variant of this invention is the use of a flexible wall attachedto a rigid or semi-rigid disk end cap, as depicted in FIGS. 4, 5, 6 and7. FIGS. 4 and 5, depict a flexible cylindrical or conical wall of aninternal container, attached at one end to the rigid wall of theexternal tank and attached at the other end to a disk end cap. The diskand walls having the ability to keep the two liquids separate and thedisk can travel from the bottom to the top of the tank. The flexiblesection can be attached to the upper or lower section of the tank wall,however, in using this configuration it is preferred that the attachmentpoint is centrally located to minimize the materials of construction,which is achieved because only half the height of flexible tank wallneed be installed to enable spanning from the tank top to the floor. Itis also preferred that the disk and walls be suitably ballasted togreatly neutralize any density differences between the intended storageliquids. Such ballasting can be dynamically adjusted by adding orremoving fluids from small bladders attached to the inner tank or tanks.Wherein, the fluid used is of either a significantly higher or lowerdensity that the liquid it displaces. Alternatively, this ballasting canbe implemented by adjusting the length of cables connected between thetop of the inner tank and the roof of the outer tank. This dynamicballasting could also be integrated with self-contained level sensingtransmitters and/or inclinometers, such that the disk can be leveled,and these controls or equivalent controls are applicable to allapplications of this invention. Such sensors may be encapsulated orotherwise sealed and may include small, two or three axis, inclinometerchips and miniaturized transponders programmed to send data whenrequested or at infrequent times or if pre-set limits are exceeded.Using current technology, these devices could be powered continuouslyfor over fifteen years using small lithium batteries. A transponder anddata processing unit external to the tank could be used to analyze thesensor data and activate valves, pumps or winches as needed to adjustthe inner tank's buoyancy or inclination as appropriate. Another meansof accomplishing the same goal may include similarly sealed and poweredelectronics that respond to a signal emitted from some reference pointwithin the tank. The response delay from each of the sensors would allowdetector units to triangulate their locations, and the results used toeffect the buoyancy as described earlier or to simply monitor the volumeof the inner tank.

Aspects of the invention shown in FIGS. 4 and 5 can also use differentattachment points such as the tank roof or the base. Many petroleumtanks are constructed with an internal floating-roof, and FIG. 6 depictsan arrangement wherein the end cap disk is attached to a flexible,circular wall, which is attached at the other end to the floating roof18. This example also depicts one method of plumbing the secondarycontainment volume, by using an articulated arm drain, which is not anuncommon technique in the petroleum industry for draining floatingroofs. Further development of this concept could also be comprised of anattachment of flexible walls to a floating annulus, which may beseparate from any roof structure.

FIG. 7 shows a concept similar to that in FIG. 4, when attached to thetank's base, which greatly simplifies the external plumbing logistics.Here the flexible walls are shown connected to a flexible disk, but thedisk and walls can be comprised of any combination of flexible and rigidcomponents. Furthermore, as depicted in FIG. 8, the arrangement caninclude additional flexible walls 80, and 81, between the rigid tankwall and the inner, second tank, respectively. The third and/or fourthwalls can be inflated with a separate fluid to enable the bulk of theprimary storage tank to be drained below the level of the secondarycontainment, while minimizing stress on the secondary containment walland avoiding contact or shear against the rigid tank wall.

In a particularly useful aspect of the invention, internal secondarycontainer can be comprised of a free-form bladder shape that can befilled and emptied from pipe work attached to the tank walls, base orfrom above. This bladder may be composed of a membrane with sufficienttensile strength and chemical compatibility to ensure long termseparation of the liquids. This bladder may be constrained as shown inFIG. 2 within the outer tank 3 by a variety of means such as porous wall70, such that hydraulic pressure and turbulence generated during thefilling (or emptying) of the tank does not overly stress the bladder 15having liquid 13 contents or its connections.

In such an embodiment of the invention, the bladder will be fabricatedwith a flexible membrane that can comprise a fiber reinforced polymersuch as urethane, which may or may not include a metallic or otherimpervious inner layer. It is understood that the bladder need not beentirely flexible and may contain sections of non-flexible materials orcomponents. The support is typically a porous wall but can also comprisea rigid wall of perforated metal or other suitable polymer or compositematerial, or comprise of a flexible wall such as a chain-linked fence orequivalent mesh like material that is suitably restrained to minimizecontact with the inner wall of the outer tank. Such a restraint may beinclude a material having a very low level of rigidity such as anopen-cell foam similar to that used for safety in gasoline tanks ofracing cars. Clearly, many structural combinations of this invention canbe developed by those skilled in the art, without detracting from thenovelty or benefits of the invention.

It is understood that the present invention also comprehends the use ofwireless sensors capable of monitoring the position or orientation ofthe bladder. Additionally, buoyancy adjusting devices attached to thebladder or associated piping can also be utilized. For instance, thebladder's upper and lower surfaces be suitably ballasted to greatlyneutralize any problematic density differences between the intendedstorage liquids and to adjust the bladder's attitude. Soon ballastingcan be dynamically adjusted by adding or removing fluids from smallbladder compartments attached to bladder's surfaces. Wherein, the fluidused is of either a significantly higher or lower density that theliquid it displaces. Alternatively, this ballasting can be implementedby adjusting the length of cables connected between the top of the mainbladder and the roof of the outer tank. This dynamic ballasting couldalso be integrated with self-contained level sensing transmitters and/orinclinometers, such that the disk can be leveled, and these controls orequivalent controls are applicable to all applications of thisinvention. Such sensors may be encapsulated or otherwise sealed and mayinclude small, two or three axis, inclinometer chips and miniaturizedtransponders programmed to send data when requested or at infrequenttimes or if pre-set limits are exceeded. Using current technology, thesedevices could be powered continuously for over fifteen years using smalllithium batteries. A transponder and data processing unit external tothe tank could be used to analyze the sensor data and activate valves,pumps or winches as needed to adjust the bladder's buoyancy orinclination as appropriate. Another means of accomplishing the same goalmay include similarly sealed and powered electronics that respond to asignal emitted from some reference point within the tank. The responsedelay from each of the sensors would allow detector units to triangulatetheir locations, and the results used to affect the buoyancy asdescribed earlier or to simply monitor the volume of the inner tank.

1. A multi-product storage tank comprising: (a) a first tank shellcomprising a bottom and a side wall extending upwardly from the bottomthereby adapting the shell to contain liquid; (b) a second tank disposedwithin the first tank wherein the second tank comprises at least onepartially rigid end cap and flexible, fluid-tight, membrane side wallattached to the end cap thereby defining a first space between the firsttank shell and the second tank wherein a first liquid can be stored inisolation from the contents at the second tank.
 2. The multi-producttank of claim 1, wherein the second tank comprises two end caps whereone or both of the end caps comprises a rigid outer annulus.
 3. Themulti-product tank of claim 1, wherein the second tank is restrainedfrom direct contact with the side wall of the first tank shell.
 4. Themulti-product tank of claim 1, wherein the second tank is disposedwithin a porous and or flexible support means positioned between thesecond inner tank and the side well of the first tank shell, wherein thesupport means is adapted to restrain the second tank from direst contactwith the side wall of the first tank shell.
 5. The multi-product tank ofclaim 1, wherein the second tank has its attitude monitored and adjustedto ensure stable floating dynamics.
 6. A multi-product storage tankcomprising: (a) a first tank shell comprising a bottom and a side wallextending upwardly from the bottom thereby adapting the shell to containa first liquid; (b) a support means disposed within the tank shell andfixed to the tank shell; and (c) a flexible, fluid-tight bladderdisposed within the support means, wherein the flexile bladder isadapted to storing a second liquid, thereby defining a first spacebetween the first tank shell and the flexible bladder wherein a firstliquid can be stored in isolation from the contents of the bladder. 7.The multi-product tank of claim 6 wherein the tank further compriseswireless sensors capable of monitoring the position or orientation ofthe bladder.
 8. The multi-product tank of claim 6, wherein the tankfurther comprises buoyancy adjusting devices attached to bladder or anypiping associated with the bladder.
 9. The multi-product tank of claim 6wherein the support means comprises a ridged porous wall.
 10. Themulti-product tank of claim 6 wherein the support means comprises aflexible wall.